1. Field of the Invention
The present invention relates to a method for driving display devices having discrete fixed pixel arrays such as liquid crystal units, plasma units and electroluminescent (EL) units, and a display device itself.
2. Description of the Related Art
Electronic display devices can be regarded as electronic devices for visually communicating a variety of information from various kinds of electronics to humans, or as electronic tools for electronic and visual exchange of information between humans. Electronic display devices in information-intensive society are widely used in various application areas, whether industrial or for consumer use, and are playing very important roles.
Recently, liquid crystal displays, plasma displays and electroluminescent displays have become objects of active research and development initiatives as electronic display devices to replace CRTs. Further, for example, attempts are being made to realize flat-type large display units with a 40 to 60 inch screen, such as liquid crystal projectors and plasma display units, using a high definition (HD) system.
However, display devices having discrete fixed pixel arrays and driven by a line sequential system, such as liquid crystal displays, plasma displays and electroluminescent displays, have a problem of being unable to simply comply with interlaced scanning when an NTSC color television system or a HD (particularly the so-called xe2x80x9cHigh Visionxe2x80x9d) system is to accomplish displaying by interlaced scanning. This problem is addressed by equipping the display device itself with a progressive circuit compatible with interlacing or by converting video signals into a non-interlace format by using memories and displaying the converted signals, but these solutions involve an expensive and complex system.
Further, in this case, the display device requires as many pixels, particularly as many vertical pixel lines, as the effective scanning lines of video signals, but, if the display device has only a smaller number of pixe lines than the effective scanning lines, such expediencies are resorted to as writing the odd field (a first field) and the even field (a second field) into the same pixel, or skipping some video signals when writing in. These expediencies result in a poorer vertical resolution of the display screen and inferior picture quality than the original video signals could otherwise provide.
As a possible solution to this problem, a display pixel shifting technique (the wobbling technique) is known as a way to enhance vertical resolution using the same pixels in a display unit having display elements consisting of discrete fixed pixels (see the Japanese Patent Laid-Open Publications Nos. 7-64046 and 7-104278).
This wobbling technique is a method whereby one field picture is displayed in a position different from another field picture by switching the optical axis of the first field scanning and that of the second field scanning with the phase modulation optical elements and a birefringent medium.
However, in the methods described in the Japanese Patent Laid-Open Publications Nos. 7-64046 and 7-104278, the vertical optical axis shift, in other words the enhancement of vertical resolution, is made possible by using signals synchronized with interlacing in the first and second fields, but the horizontal resolution of display cannot be enhanced more than the number of pixels allows, even if the video signals have a broad band, because the resolution of fixed pixels is restrained by their number.
Thus, enhancement of the horizontal resolution of a display device having discrete fixed pixel arrays such as a liquid crystal display unit has its inevitable limit because the horizontal resolution is restricted by sampling and, therefore, displaying of interlace signals as they are would only result in displaying of the same picture shifted in the horizontal direction.
The present invention has been attempted in view of the above-described circumstances, and its object is to provide a method for driving a display device and a display device itself having display elements with fixed pixel arrays, permitting interlace display and enhancement of the horizontal resolution in particular.
The inventors of the present invention, in their dedicated pursuit of a solution to the above-mentioned problem, have found that when high resolution is to be realized in interlace display or the like with display elements having discrete fixed pixels and wobbling elements, interlace display is made possible and high resolution realized by shifting the timing of sampling while scanning a first field (the odd field, for example) and that of sampling while scanning a second field (the even field, for example) by a period of time corresponding to the amount of pixel shift resulting from wobbling and the sampled signal to the above-described display elements with the shifted timings.
Thus, the present invention pertains to a method for driving a display device (hereinafter called the invented driving method), said display device comprising:
display elements having discrete fixed pixels; and
wobbling elements for wobbling a light beam emitted from said display elements; wherein:
when the display device is to be driven, the timing of sampling while scanning a first field and that of sampling while scanning a second field are shifted by a period of time corresponding to the amount of pixel shift resulting from wobbling and the sampled signal to said display elements with the shifted timings.
According to the invented driving method, when a display device comprising said display elements and said wobbling elements is to be driven, interlace display or the like compatible with the NTSC system or the HD system can be realized with high resolution, because the timing of sampling while scanning the first field and that of sampling while scanning the second field are shifted by a period of time corresponding to the amount of pixel shift resulting from wobbling (i.e. the period of time required for wobbling) and applying the sampled signal to said display elements with the shifted timings.
In particular, since the invented driving method makes possible realization of interlace display or the like with high resolution, especially in the horizontal direction, by merely shifting the timing of sampling while scanning the first field and that of sampling while scanning the second field by a prescribed period of time (phase), compatibility with the NTSC system or the HD system can be achieved without having to modify hardware configuration, such as providing progressive circuits compatible with interlacing. Furthermore, since pixel shifting in an oblique direction (hereinafter, it may be called oblique wobbling) is made possible, even higher resolution can be realized.
Furthermore, the present invention provides a display device capable of realizing the inventive driving method (hereinafter called the invented display device) comprising:
display elements having discrete fixed pixels;
wobbling elements for wobbling a light beam emitted from said display elements;
a timing generating circuit for shifting the timing of sampling while scanning a first field and the timing of sampling while scanning a second field by a period of time corresponding to the amount of pixel shift resulting from the wobbling; and
driver circuits for driving said display elements and said wobbling elements in each of said fields with timing signals generated by the timing generating circuit.
The invented display device, since it comprises:
display elements having discrete fixed pixels, such as liquid crystal, plasma or electroluminescent elements:
wobbling elements for wobbling a light beam emitted from these display elements;
a timing generating circuit for shifting the timing of sampling while scanning a first field and the timing of sampling while scanning a second field by a period of time corresponding to the amount of pixel shift resulting from the wobbling; and
driver circuits for driving said display elements and said wobbling elements in each of said fields with timing signals generated by the timing generating circuit, makes possible interlace display or the like compatible with the NTSC system or the HD system, particularly with high resolution, by merely shifting the timings of sampling in the timing generating circuit by a prescribed period of time without having to modify the hardware configuration of the display device.